(Photo by Joe Robbins/Getty Images)

Rafael Soriano got his 25th save of the season last night, his 200th for his career, making him the 46th reliever in history to reach that milestone.

And while we have historical context that Soriano is one of the best closers in the game, what may be overlooked is that he is also the best closer in the National League this season.

Yes, Trevor Rosenthal has the most saves (32) and Huston Street, before being traded to the Los Angeles Angels, has the lowest ERA (1.09), but none has saved more runs based on the bases occupied and out situations faced than Soriano has.

Base-Out Runs Saved, or RE24, measures how many runs a pitcher saved or cost his team based on his numbers of singles, doubles and all other events allowed including outs.  It also considers the situations in which these events happened.

The basic idea is that you are interested in the 24 base-out states, and the outcome of the performance in each of the particular states. A HR with bases empty has a different impact than a HR with men on base. A strikeout with a runner on 3B with less than two outs is hugely impactful, while with no one on base, it is no different than any other out.

Here is the top 10 for the National League as of Sunday’s games.

Soriano has always been a reliable closer, but here are three reasons why he has taken things to another level:

Opponents are hitting his breaking ball for less power

Soriano is throwing his slider almost twice as often as he did last season and opposing hitters are having trouble adjusting: They have managed a mere .218 batting average against with just four extra-base hits in 55 at bats for an isolated power of .109 – much lower than the .234 hitters tallied last season.

Batters are swinging and missing more fastballs

In addition to a more effective slider, batters are having trouble dealing with his fourseam fastball. Batters have just 10 hits in 407 pitches (.133 batting average against) and are swinging and missing at a higher rate than at any time in the past four years.

More groundballs, less line drives

They say the ground ball is a pitcher’s best friend. In the National League, hitting a grounder results in a 0.504 on-base plus slugging while a line drive have averaged nearly double that (1.000 OPS). Soriano is inducing more groundballs this season and less line drives, which is helping keep his ERA low (1.10) and runners stranded on base (89.9 percent).

Rafael Soriano batted balls in play (Source: Fangraphs)

Saves and ERA can give us an idea as to who is performing well, but RE24 illuminates a pitcher’s true value, and right now, no closer is more valuable to his NL team than Soriano.